select
EMP_CODE AS CODE,
EMP_LAST_NAME AS SURNAME,
EMP_FIRST_NAME as NAME
from 
EMP
where
EMP_LAST_NAME || EMP_FIRST_NAME in(
SELECT EMP_LAST_NAME || EMP_FIRST_NAME
FROM EMP
GROUP BY EMP_LAST_NAME || EMP_FIRST_NAME
)
AND
VALID_FLG = '1'

Order By 
REPLACE(EMP_LAST_NAME,' ','') asc,
EMP_CODE asc